Originally Posted by boatless
Here is how to build a discharge graph using the USGS website:
1) open the site you're interested in
2) click on "Summary of all availbel data for this site"---this is just below the parameter box at the top of the page
3) select daily data from the available data
4) select "graph" as the output format and enter the Begin and End dates on the left. Note that the pop-up calander feature does not work (at least with explorer) you must enter the date range manually.
5) press go and enjoy
This works for daily discharge but does not work for average flow by month as the poster asked for.
In mine I should have suggested the OP use bar or column as opposed to line (at least makes more sense to me)